SACRAMENTO — Leading legislators on Tuesday, joined by the billionaire investor who spent $26 million to help get Proposition 39 passed, announced a plan to spend hundreds of millions of dollars from the measure to improve energy efficiency at California's aging schools.

Proposition 39, overwhelmingly approved by voters last month, will generate an estimated $1 billion a year in additional tax revenue from out-of-state corporations that no longer can employ an advantageous formula for calculating profits upon which they pay California state income taxes. Instead, they must use the same formula as companies either based in California or with substantial operations here.

For the first five years, the measure requires that half the new revenue be spent to improve energy efficiency at public buildings, and gives the Legislature authority to determine how to do it. Sen. Kevin De Leon, D-Los Angeles, co-chairman of the Proposition 39 campaign, wasted no time in laying out a proposal. He submitted it as Senate Bill 39 when the Legislature convened on Monday.

De Leon said the emphasis will be on improving K-12 schools.

"We're giving voters what they asked for," he said. "They asked for jobs and they asked for energy savings in our classrooms."

De Leon was joined at a news conference Tuesday at a Sacramento elementary school by Senate President Pro Tem Darrell Steinberg, D-Sacramento, and venture capitalist Tom Steyer, the principal funder of the initiative.

"We always wanted to make sure we got bang for the buck," Steyer said. "Energy efficiency is low-hanging fruit. The returns are good."

De Leon estimated that as many as half of California's approximately 10,000 schools could receive assistance for projects, such as new lighting and improvements to heating and air-conditioning systems. His bill envisions a competitive application process that would be administered by the Office of Public School Construction, an existing state agency that now administers state school-construction bonds.

He noted that the Los Angeles Unified School District alone spends $109 million annually on energy costs, meaning that a 20 percent improvement in efficiency would yield an additional $20 million a year that could be spent in classrooms.

Just as important, he said, is that efficiency projects are labor intensive and will create jobs for electricians, carpenters and other construction workers. "This is work that must be performed on site, creating jobs that can't be outsourced to other countries," he said.

With more than $2 billion at stake, there will be competing ideas concerning how to spend the money.

Assemblyman Das Williams, D-Santa Barbara, on Monday introduced legislation that proposes using some of the Proposition 39 money to establish a revolving loan fund that universities and community colleges could access to pay for energy-efficiency projects at buildings on their campuses.

De Leon said Williams' proposal isn't necessarily in conflict with his proposal, indicating he is open to considering using some of the money at college campuses. "It's the beginning of the legislative process," he said.

Steinberg, however, made clear his preference for targeting the money for K-12 schools. "Focus is the right way to approach the implementation of this initiative," he said.

Such a focus, Steinberg said, would yield a dual benefit to the state by freeing more money to be spent directly on education and produce a clear result that would be evident to voters.

"The danger with programs in the past is that we spend a little bit here, a little bit there, and then people ask what was accomplished," he said.

Also participating in the news conference were Superintendent of Public Instruction Tom Torlakson and Sen. Fran Pavley, D-Agoura Hills.

"U.S. public schools spend more on utility bills than on textbooks and computers combined," Pavley noted. "That's the wrong priority."